President Nicolas Sarkozy, seeking to combat the radicalization of French Muslim youth, said heâll ban hard-line clerics from entering France as investigators deepened a probe into whether the Toulouse killer acted alone.

Sarkozyâs response to the murders hasnât helped him narrow the gap against Socialist Francois Hollande, with the presidential vote less than a month away, three polls today showed. Sarkozy announced the ban measure as investigators yesterday reviewed the activities of the killerâs brother Abdelkader Merah before the attacks that left seven people in the Toulouse area, including three Jewish children, dead.

Abdelkader helped his 23-year-old brother Mohammed Merah steal the scooter used to escape from the sites of the attacks, bought his helmets, and was located by his mobile-phone network near the Jewish school several times in the days before the shootings, France 2 television reported, citing police officials. Abdelkader was indicted by an anti-terror judge on charges of complicity on March 25. He denies any involvement.

âThere are still gray areas in this investigation, which has just started,â Frederic Pechenard, the head of the national police, said in an interview yesterday on RTL Radio, adding that investigators are still unsure whether Merah acted alone.

Sarkozy said yesterday heâd prevent Yusuf al-Qaradawi, a Muslim theologian with a widely watched Al Jazeera television program, from entering France for a conference next month. He today called on called on television stations not to broadcast the video of the killings. The gunman filmed all his attacks, with the content of the camera âextremely explicit,â the French prosecutor investigating the case said last week.